1. Field of the Invention
The present invention relates to a bulb socket for a wedge base bulb for use in an automobile lamp device and, in particular, to such bulb socket which is improved in the structure of a connecting terminal to be insert molded into the bulb socket and a method for manufacturing the same.
2. Related Art
Conventionally, as a bulb socket which is used for connection of lamp devices in an automobile or the like, there are known various bulb sockets. As an example of the conventional bulb sockets, description will be given below of a bulb socket which is disclosed in Japanese Patent Publication No. Hei. 9-17533 (Shinji).
That is, in a conventional bulb socket 31 shown in FIG. 6, a bulb insertion portion 41 and a connector plug portion 46 are disposed in an L-shaped manner. At first, as a portion which corresponds to the bulb insertion portion 41, there is molded a bottomed and cylindrical-shaped cylindrical body 34. The cylindrical body 34 is formed in such a manner that a connecting terminal 36 formed of a conductive body such as a phosphor bronze plate or the like is inserted into the mother structure of the cylindrical body 34 and then the mother structure is molded of insulating molding material such as nylon resin together with the thus inserted connecting terminal 36.
As shown in FIG. 7, the connecting terminal 36 includes a wall plate portion 36a which extends along the inner wall surface of the cylindrical body 34 and, a portion of the wall plate portion 36a is inwardly cut and raised to thereby provide a hold piece 36b in such a manner that it can be flexed and deformed; that is, the hold piece 36b can be contacted with the side surface of a wedge base bulb disposed opposed thereto, thereby preventing the play or free motion of the connecting terminal 36. Also, one side edge of the wall plate portion 36a is bent at right angles to thereby provide a pair of mutually parallel arranged elastic contact piece 36d and elastic securing piece 36c which respectively function as electrode terminals. Further, in the connecting terminal 36, there is provided a contact tab 36e which is projected from the end edge of the portion of the wall plate portion 36a in which the elastic contact piece 36d is provided. The contact tab 36e is formed in the following manner: that is, after it is inserted into and projected from the cylindrical body 34, it is bent at right angles and the leading end thereof is then projected into the connector plug portion 46.
Referring further to an outer shell body 33 shown in FIG. 6, the outer shell body 33 is formed of the same material as the cylindrical body 34 and includes a square-cylindrical-shaped outer cylinder 40 which is used to cover the outer side surface and bottom surface of the cylindrical body 34, while the cylindrical body 34 and outer cylinder 40 cooperate together in forming the bulb insertion portion 41.
In the bulb insertion portion 41 of the bulb socket 31, if the wedge of the bulb is contacted with the elastic contact piece 36d of the connecting terminal 36 and is also secured to the elastic securing piece 36c thereof, and, at the same time, if a mating connector connected to a power source system is inserted into the connector plug portion 46, then the contact tab 36e comes into contact with its mating connecting terminal, so that the bulb can be connected to the power source system electrically.
Next, description will be given below of a procedure for molding the bulb socket 31. At first, the cylindrical body 34 is primarily molded using a metal mold (not shown). Next, the thus molded cylindrical body 34 is set within another metal mold for molding the bulb socket 31 and is then insert molded together with the bulb socket 31 within the metal mold. That is, firstly, the connecting terminal 36 is set within a separate metal mold and molding material is then poured into the present metal mold to thereby mold the cylindrical body 34; and, next, the cylindrical body 34 is set as a core in a metal mold for molding the outer shell body 33 and is then insert molded there, so that the bulb socket 31 can be molded.
Accordingly, the shape of an in-flow preventive core used to prevent the molding material from flowing into a bulb storage portion 49 in which the elastic contact piece 36d, elastic securing piece 36c and hold piece 36b are located can be so formed as to have a relatively simple structure, and such simple structure is capable of coping easily with a change in the design of the bulb storage portion 49 as well.
Also, since the connecting terminal 36 has been already molded as a core within the outer cylinder 40 at the time when molding the outer shell body 33, there is no possibility that the inflow pressure of the molding material can bring down and deform the metal plate of the connecting terminal 36 inwardly to thereby manufacture an inferior or defective bulb socket.
However, in the above-mentioned conventional bulb socket 31, since the outer cylinder 40 core portion and the outer shell 33 portion must be molded in two stages, the number of man-hour is large, which results in the lowered operation efficiency and increased manufacturing cost of the bulb socket.
Also, when the bulb socket is a small-sized one, the connecting terminal is so formed in structure as to include three U-shaped side plates and a bottom plate and, inside the two mutually opposed side plates, there is interposed an elastic contact piece which can be contacted with a bulb wedge. When molding the bulb socket, if the bulb storage portions of two connecting terminals are insert molded while they are opposed to each other, then the molding material is prevented from flowing into the bulb storage portions.
However, in the connecting terminal of a bulb socket for a large-sized wedge base bulb, an elastic contact piece and an elastic securing piece are provided on one side wall of the connecting terminal. Therefore, the above-mentioned structure of the bulb socket for the small-sized bulb cannot be applied as it is to the large-sized bulb.